I wanted to get myself a Mantis microscope for a few years now. This time I finally gave in and bought one. Professional microscopes can get very expensive very quickly. Therefore I want to talk about where and why money can be saved. In the second part of the post, I will describe the process of building a battery pack that can be used instead of the intended DC adapter.
Company Vision Engineering produces multiple families of microscopes, varying in application, maximum zoom, included options and accessories, and price. When choosing a microscope for electrical engineering there are only 2 products I would realistically want. Mantis Elite or Mantis Compact. They both offer incredible image quality, are fully optical and work on patented stereo technology. Meaning you see the object move as you turn your head. The main difference between them is the price. They also use different lenses. Other than that, I did not find any differences. In fact, I wonder, based on my findings further down in the post, if Elite lenses would work with the Compact series.
I was trying to get the microscope for as cheap as possible. That is why I opted for Mantis Compact. Looking trough the brochure I also figured out it is possible to order each part of the scope separately. So only bought the head and two lenses (4x and 8x). Everything else I can make myself.
I spent around 1170€ for the head and 600€ for the lenses with caps (always get the caps!). The cheapest stand would cost me another 800€ and what hurts the most – the power supply is almost 90€!!! For a 9V adapter!
The stand and the power supply
The cheapest stand is very limiting in the motion it provides. It only moves up and down, and its base can rotate. For my setup, this would be useless. The stand I would want was about 3.5 times the price of the cheapest one. Instead, I found and bought a computer monitor arm. It is way more configurable than the basic stand. It approaches the top-shelf version, even surpassing it in some ways. With this arm, the microscope can be moved anywhere just by holding the head. I imagine the proper stand offers more rigidity though. This one only costs around 100€ on Amazon – can’t beat that. The only thing you need to do is make your own mount for the Mantis head instead of the monitor. But that can be done in an hour from some aluminum U profile. I really recommend this solution for microscope mounts to everyone.
Regarding the power supply, I carefully disassembled the head and looked at the circuit. It is much simpler than I had imagined. There is only a DC power plug, 20 LEDs and 20 current limiting resistors. Their value is surprisingly low. Only 68 ohms. At 9V the current is around 40mA per LED. This did not sit right with me. There is absolutely no need for the current to be so high. The LEDs reach full brightness at 10mA. I am glad I did not buy the overpriced power supply from the manufacturer. I recommend anyone with a Mantis microscope to use a 5V power supply. Another thing I found interesting is that the manual says not to connect the power supply directly to the head…
I had several options to move forward: buy a cheap adapter or make my own adapter, decide whether to make the brightness variable or not, determine where to place the power switch—either where the stand mounts to the table or at the head? Should I use push buttons or switches? In the end, I decided to make a battery pack. 4V from Li-ion batteries is perfect. The voltage has no noise. The current trough each LED is around 15mA. And I avoid the cable running down the arm and into the wall. I am using two 18650 Li-ion batteries, a simple Chinese TP4056 charging module and a switch.
Everything is packed inside a small 3D printed enclosure. I had difficulties making it fit nicely around the body but I am pretty happy with the end result. The .stl files are attached in a zip archive at the bottom of the post.
Battery pack assembly
- Solder or spot weld appropriate length wires to the batteries.
2. Insert the charging module in the 3D printed enclosure. Secure it with the provided clamp piece. Do not forget to replace the original LED indicators with 3mm diodes. It’s a little bit of a surgery but can be done.
3. Insert the batteries into the enclosure and solder the wires to the charging module.
4. Mount the switch and the power cable. The switch should be oriented in a way that up motion turns on the device. Solder all connections, ensuring the switch connects or disconnects the positive wire.
5. Mount the base plate to the back of the mantis head.
6. Attach the rest of the enclosure with 4 screws and connect it to the head with a DC plug.
